This invention relates to a method of producing magnetosensitive semiconductor devices and more particularly to such a method by which devices with improved sensitivity can be assembled easily and their substrates are not cracked easily.
FIGS. 3-5 show conventional assembly methods of a semiconductor chip and a magnetic piece which are prepared separately to produce a magnetosensitive semiconductor device such as a Hall element with improved sensitivity. According to the method shown in FIG. 3, a magnetic piece 2 is bonded onto a leadframe 1 and a semiconductor chip 3 such as a Hall element is bonded onto this magnetic piece 2. According to the method shown in FIG. 4, a semiconductor chip 3 is bonded onto a leadframe 1 and a magnetic piece 6 is bonded onto this semiconductor chip 3. According to the method shown in FIG. 5, a magnetic piece 2 is bonded onto a leadframe 1, a semiconductor chip 3 is bonded onto this magnetic piece 2 and then another magnetic piece 6 is bonded onto this semiconductor chip 3. In FIGS. 3-5, numerals 31 each indicate a magnetosensitive part of the semiconductor chip 3, numerals 4 indicate a terminal wire, and numerals 5 indicate a package resin. These methods, however, involve complicated assembly processes and do not effectively improve device sensitivity.
In order to improve the device sensitivity by using a magnetic piece, it is necessary to make it thick or to place it near the magnetosensitive part 31 of the semiconductor chip 3, but the thickness of the magnetic piece is limited by the size of the package. As for the placing of the magnetic piece near the magnetosensitive part of the semiconductor chip 3, there is a limit imposed by the thickness of the semiconductor chip 3 if the magnetic piece 2 is disposed below the semiconductor chip 3 as shown in FIGS. 3 and 5. Since the semiconductor chip 3 must be thick enough such that the semiconductor substrate will not easily crack when processed to form the magnetosensitive part 31 of a Hall element or the like. For this reason, its thickness must be greater than 200 .mu.m. Even if the product is to be handled very carefully, a minimum of 150 .mu.m is required.